The present invention relates in general to exhaust extraction systems for emergency vehicles, such as a fire truck or ambulance. More particularly, the present invention relates to the design of a locator ring which is designed to fit over the exhaust system tail pipe of an emergency vehicle and a nozzle assembly which magnetically attaches to the locator ring.
Emergency vehicles, such as a fire truck, create an interesting exhaust-removal challenge due to the nature and manner of use of the vehicle in preparation for an emergency run. A fire truck is usually backed into the fire house garage bay and readied for its next run in this manner. When an alarm call comes in, the engine of the fire truck is started by the driver while he waits for everyone to prepare the equipment and get on board. During this brief time interval before the truck leaves the station, the engine is cold and generates the dirtiest exhaust gases which need to be vented to the outside atmosphere.
The exhaust system of a fire truck is typically arranged so that the "tail" pipe exits from the right side of the truck in front of the rear axle. While this location places the exiting exhaust gases near the center of the fire house, it is an advantageous location for present day exhaust extraction systems. For the most part these present day exhaust extraction systems use a flexible exhaust hose which is connected at one end to the fire truck exhaust pipe and at the opposite end to an overhead duct which leads out of the fire house. A high pressure blower is used to forcibly remove the exhaust gases from the fire house. A hose adapter or nozzle assembly of some type is typically used to connect the flexible hose to the exhaust pipe. With secure and sealed connections and so long as there are no perforations or open seams in the exhaust extraction system, all of the vehicle exhaust gases will be safely vented out of the fire house and into the atmosphere.
The use of a flexible hose to remove exhaust gas from a running engine is not new. Automobile mechanics have used such hoses for years. However, there is one important difference between use by a mechanic and use as part of an exhaust extraction system which is attached to an exhaust pipe of a fire truck. Once everyone is onboard the fire truck, it is ready to leave the fire house and there is usually no one left to disconnect the exhaust hose from the exhaust pipe. Even if personnel were left behind, safe handling of the vehicle exhaust would dictate that the vehicle be pulled out of the fire house and then have the hose removed. This would involve a start up and stop procedure at the very time the fire truck is trying to leave quickly on the emergency run. Even if someone was left behind and could disconnect the exhaust hose prior to the fire truck departing, this would allow exhaust gas to be dispersed into the fire house, the very event which exhaust extraction systems are designed to prevent.
In order to address this disconnect concern, present day exhaust extraction systems try to provide an automatic disconnect feature such that the adapter or nozzle connecting the flexible hose to the exhaust pipe comes off automatically after the fire truck has actually left the fire house. While present exhaust extraction systems which are offered commercially have approached this design challenge in slightly different ways, most systems provide an extra length of flexible hose which is held by a saddle and suspended from an overhead track by means of a spring-biased balancer. The spring-biased balancer supports the hose and the induced spring-tension force facilitates the release of the hose from the exhaust pipe as the fire truck leaves the fire house. As the fire truck begins to pull out of the fire house, the distance between the exhaust pipe and the duct work connection increases. This pulls on the flexible hose which in turn pulls the balancer down the track toward the door. The loop of excess hose between the balancer saddle and the duct hose connection allows this movement. When the balancer reaches the track stop, the balancer cable begins to uncoil which increases the resisting spring force. At some point, the resisting spring force of the balancer becomes greater than the force needed to separate the adapter from the exhaust pipe. Continued travel of the fire truck causes the hose adapter/nozzle to separate from the exhaust pipe.
The following companies have offered exhaust extraction systems which, for the most part, can be said to function in the manner which has been described: Harvey Industries, Inc., 1340 Home Avenue, Buildings F and G, Akron, Ohio 44310-2580; Nederman, Inc., P. O. Box 278, McBee, S.C. 29101, Westland, Mich.; Tykron, 241 South Service Road, Grimsby, Ontario L3M 1Y7, Canada; Plymovent, 375 Raritan Center Parkway, Edison, N.J. 08837; and Exhaustomatic, Inc., P. O. Box 503444, Indianapolis, Ind. 46250.
While many of the exhaust extraction systems offered by these listed companies are directed to solving the same problem, and while they can be said to generally perform in the same way, there are various design differences and different features which are offered. The overhead track and duct components, the balancer and the flexible hose are fairly well developed and would be considered as fairly mature technology. The "tail" pipe adapter though is an area of greater design attention. The desire is to provide a design which can be easily and securely attached to the exhaust pipe in order to connect the extraction system and yet release in a predictable and reliable manner without damage to the nozzle adapter, flexible hose, or the exhaust pipe, or for that matter any other portion of the vehicle or fire house.
The exhaust extraction system of Harvey Industries, Inc. connects the flexible hose to the exhaust pipe by a spring loaded clamp which is mounted on and extends through the nozzle. The nozzle is removed from the exhaust pipe when the balancer resisting spring force overcomes the clamp spring. The nozzle does not provide a seal around the exhaust pipe, but it does permit for ambient air to enter the nozzle.
An earlier exhaust extraction system which was offered by Nederman, Inc. provided an electromagnetic attachment where a magnet attached to the side of the fire truck and held the nozzle opening at the exhaust pipe height. The nozzle did not provide a seal around the exhaust pipe but it did allow ambient air to enter the nozzle. In those fire station arrangements which used front and rear doors for a pass through bay, this system was not suitable. More recently this company has created a pneumatic system.
An earlier exhaust extraction system which was offered by Tykron used a nozzle with a tension spring which rested in a groove inside the nozzle and surrounded the exhaust pipe. The nozzle spring did not provide a seal around the exhaust pipe, nor did it allow the maximum amount of air to enter in relation to its inside diameter size.
The exhaust extraction system of Plymovent uses a pneumatic bladder nozzle attachment concept. The bladder has three compartments and provides three points of pressure contact but does not form a complete seal around the exhaust pipe. The pneumatic bladder nozzle allows a very small volume of air to enter, but does not permit the maximum amount of air to enter. Consequently, with respect to the nozzle inside diameter size, this does not allow the complete system to operate at the lowest possible temperature. The described pneumatic system requires an air compressor, air filter and lubricator, air lines, controls, and the pneumatic bladder which adds to the overall cost and complexity of the system. It is believed that air leaks are a problem with this system and further, if the fire truck leaves the station at too fast a speed and the air has not been bled out of the nozzle bladder, the flexible hose can be damaged. Since there is a partial seal on the exhaust pipe, this can cause a two cycle turbocharger on a diesel engine to rotate without lubrication when the exhaust blower operates and all engines connected to the system are not running.
The exhaust extraction system of Exhaustomatic, Inc. actually has four variations as far as securing the nozzle to the exhaust pipe. Their product literature indicates that the four nozzle designs include a clamp design, permanent magnet design, electromagnetic design, and a pneumatic design. It is believed though that in these designs the nozzle does not provide a complete seal on the exhaust pipe. However, these designs do allow ambient air to enter and provide some system cooling, except when the pneumatic nozzle is used.
With these earlier designs defining the state of the art in the early 1990's, the invention of U.S. Pat. No. 5,609,298 was conceived. U.S. Pat. No. 5,609,298, which issued Mar. 11, 1997 to Hyslop, discloses a magnetically-attached exhaust nozzle assembly which includes an annular nozzle locator ring which is designed to slide over and secure to the exhaust pipe of a fire truck. The nozzle locator ring includes an inner sleeve which fits closely against the outside diameter of the exhaust pipe and an outer sleeve which receives a flexible exhaust nozzle. The exhaust nozzle is integrally connected with a flexible hose of the extraction system and establishes sealing engagement at two locations on the nozzle locator ring. There is axial sealing by abutment up against a flange of the nozzle locator ring and circumferential or radial sealing due to the fit of the nozzle on the outside surface of the outer sleeve. The flexible exhaust nozzle includes a guide rail which helps with the initial alignment and a magnet housing which ultimately attaches by magnetic attraction to the surface of the exhaust pipe for securely holding the nozzle in position. A spring-biased locator pin helps to keep the magnets of the magnet housing spaced from the exhaust pipe during initial assembly.
The '298 Hyslop patent recognizes that what is desired from this type of invention is a nozzle design which readily and easily attaches to the vehicle exhaust pipe in a properly aligned fashion. Also recognized by the '298 Hyslop patent is the desirability of a quick disconnect between the nozzle and the nozzle locator ring without any undue load or stress on any portion of the vehicle or on any portion of the exhaust extraction system. According to the teachings of the present invention, improvements have been made to the device described in the '298 Hyslop patent. These improvements make the connection assembly disclosed herein easier to use and these improvements provide a more reliable structure.